This invention relates generally to the material handling art and, more particularly, to apparatus for loading and unloading superimposed sheets of glass onto and from glass shaping molds.
In the production of bent laminated glass products, such as present-day automotive windshields for example, it has been found desirable to bend the two sheets of glass forming the windshield simultaneously in order to obtain the mutual fit and conformity required for the subsequent laminating operation. The common process for achieving this is to place paired, superimposed sheets of flat glass on a gravity-type mold and heat the glass sheets to their softening point, causing the sheets to sag by gravity into conformity with the shaping surface of the mold. The two flat sheets are slightly different in size to accommodate the final curved conformation so that the marginal edges of the superimposed curved sheets lie in a substantially common plane.
The heating and consequent bending is accomplished by advancing the glass-laden molds through a furnace in which the glass sheets are heated during their travel to a point where the glass sheets are softened and caused to sag by gravity into conformity with the mold shaping surfaces. At least two attendants are required to place or load the paired sheets onto the mold prior to entry into the furnace and at least two additional attendants are required at the exit end of the furnace to remove the bent sheets from the mold. Thus, four attendants are employed to load and unload the molds on each production line of a multi-line fabricating facility. It can be readily appreciated that such manual operations seriously impair efficiency in a mass production operation while adding materially to production costs. Also, the consequent fatigue and human error in properly placing the paired sheets of glass on the mold often results in glass breakage and/or improperly shaped finished products.
In order to overcome the above-noted shortcomings, it has been found desirable to develop an apparatus for automatically loading and unloading superimposed sheets of glass onto and from bending molds. However, conventional glass sheet transfer devices, such as vacuum cups and the like, are not feasible because both sheets must be handled simultaneously. Moreover, the glass sheet surfaces must be maintained clean and free of any marking or marring so that grippers in the form of mechanical or metal fingers, tongs etc. cannot be employed.